The present invention relates to a selective release unit for a circuit breaker.
A release unit with an armature or gate and a yoke is known from the prior art. If the gate is applied, it has to shift the front gate further so that a brief high current does not result in release. The insertion of a magnet flap in a direction leading away from the magnet yoke in order to brake the magnet flap in its closing movement is also known from the prior art. It is thus possible to prevent a release in the case of brief overcurrents.
One disadvantage of prior art solutions is that in circuit breakers switched in series with one large and several small parallel circuit breakers, the disengagement of one of the small circuit breakers could possibly lead to disengagement of the large circuit breakers, such that the entire operation no longer has any current. But only the subordinate breakers should release in the case of a strong overcurrent or short circuit. For example, selectivity should be achieved in circuit breakers up to 10 kA such that no disengagement occurs with a current of 3 kA at 5 msec in large circuit breakers.
A release mechanism for a circuit breaker shown in FIG. 6 is known from the earlier German patent application No. 199 03 911.9. This breaker 1 has a moveable contact 2 that is rotatably supported on the shaft 3 of a selector shaft 4. The selector shaft 4 is itself supported in a polhode housing (not shown) and has two diametrically opposed satellite shafts 5 and 6 that are entrained around the axis 3 with a rotation of the selector shaft 4. The axis 5 is the point of application for an articulation mechanism 7 that is connected with a ratchet lever 8. The ratchet lever is pivotably supported on a shaft 10 positioned on the breaker housing 9 and is released in the case of an overcurrent or short circuit by a breaker latch 11 to enable the separated state of the contact 2 shown in FIG. 6.
The breaker latch 11 can be actuated by a release lever 13 pivotable around a rotation axis 12. The release lever 13, on the other hand, is in working connection with a release shaft 14 that is supported on a shaft 15 carried by the breaker housing 9. A lifter 16 is formed on the release shaft 14, which is pivotable against the force of a spring wound around the shaft 15 (not shown in detail here) in the clockwise direction in FIG. 6.
A magnet yoke 17 is mounted on the breaker housing 9 in the lower section of the circuit breaker and encompasses an electric rail 19 connected with the contacts of the breaker 1. An armature element 21 designed as a flap is located opposite the magnet yoke 17 and it is pivotably connected via a hinge connection 18 with a stationary section of the circuit breaker (not shown in detail). The flap 21 is also connected through a spring 20 with a stationary section of the rail 19, said spring acting on the flap in the clockwise direction. In its upper region, as shown in Figure the flap 21 is equipped with a bracket 23 permanently attached to it which, by a pivoting movement of the flap 21, can be brought into contact with the cam 16 to rotate the release shaft 14, thereby actuating the breaker latch 11 via the release lever 13 and thus initiating the disengagement process in the circuit breaker 1. Reference is made to the description of the above-mentioned German patent application for further details on this prior solution.
The purpose of the invention is to make available a selective release unit, which, if incorporated in a large circuit breaker, does not cause release of the latter if release occurs in a subordinate smaller circuit breaker.